Vulcanizable adhesive composition

ABSTRACT

A vulcanizable adhesive composition, which comprises 100 parts by weight of phenolxylylene resin or phenolbiphenyl resin, 10 to 1,000 parts by weight of resol-type phenol resin, 0 to 1,000 parts by weight of novolak-type phenol resin, 10 to 1,000 parts by weight of unvulcanized nitrile rubber and 10 to 500 parts by weight of chlorinated polyethylene, is effectively applied to (hydrogenated) nitrile rubber with a nitrile content of 18 to 48%, and has a suppression effect on a decrease in the adhesiveness even if exposed to dip in various cryogenic liquids such as flon gas, polyalkylene glycol, water, etc. for a long time.

TECHNICAL FIELD

The present invention relates to a vulcanizable adhesive composition,and more particularly to a vulcanizable adhesive composition effectivelyapplicable to vulcanization adhesion between a metal and (hydrogenated)nitrile rubber.

BACKGROUND ART

In the adhesion between a metal and nitrile rubber (NBR), adhesives ofchlorinated rubber series or novolak-type phenol resin series are used.The adhesive of chlorinated rubber series is not adhesible with a metal,so that a primer of phenol series must be applied thereto beforehand.Furthermore, owing to the high viscosity its applicability is also poor.To obtain better adhesion the primer film must have a thickness of atleast 5 μm, causing troubles in case of parts requiring dimensionalprecision, fitting parts, or the like. On the other hand, the adhesiveof novolak-type phenol series is adhesible only to (hydrogenated) NBRwith a nitrile content of 30 to 40%, so that the applicable rubber rangeis limited, and also the adhesive contains hexamethylenediamine as acuring agent, causing troubles of gas generation during the drying andbaking to foul the drier inside. Furthermore, all of these adhesiveshave a low resistance to various cryogenic liquids such as flon gases,water, PAG (polyalkylene glycol), etc., resulting in difficulty inapplication to cryogenic liquid sealing.

To solve these problems, the present applicant previously proposed avulcanizable adhesive composition comprising a resol-type phenol resin,unvulcanized NBR, chlorinated polyethylene, etc. as essential components(JP-A-6-306340 and JP-A-8-302323). However, the proposed vulcanizableadhesive composition can give a good adhesion to (hydrogenated) NBR witha nitrile content of less than 30%, but still fails to show a goodadhesion to (hydrogenated) NBR with a nitrile content of 40% or more,and has a better resistance to various cryogenic liquids than that ofthe afore-mentioned adhesives of chlorinated rubber series or phenolresin series, but still fails to meet the level of current requirement.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a vulcanizable adhesivecomposition for use in vulcanization adhesion between a metal and(hydrogenated) nitrile rubber, which is effectively applicable to(hydrogenated) nitrile rubber with a nitrile content of 18 to 48%, andwhose adhesion can be maintained without lowering even if dipped intovarious cryogenic liquids such as flon gases, polyalkylene glycol,water, etc., for a long time.

The object of the present invention can be attained by a vulcanizableadhesive composition, which comprises 100 parts by weight ofphenolxylylene resin or phenolbiphenyl resin, 10 to 1,000 parts byweight of resol-type phenol resin, 0 to 1,000 parts by weight ofnovolak-type phenol resin, 10 to 1,000 parts by weight of unvulcanizednitrile rubber and 10 to 500 parts by weight of chlorinatedpolyethylene.

Phenolxylylene resin is a polycondensation product of1,4-bis(alkoxy-methyl)benzene and phenol or a phenol derivative havingat least one methylol group at the 2,4-positions of phenol, and actuallycommercially available products, for example, MR-7800, etc., products ofMeiwa Kasei Co., Ltd., can be itself used in the present invention.Phenolbiphenyl resin is a polycondensation product of4,4′-bis(alkoxymethyl)biphenyl and phenol or a phenol derivative havingat least one methylol group at the 2,4-positions of phenol, and actuallycommercially available products, for example, MR-7850, etc., products ofMeiwa Kasei Co., Ltd., can be itself used in the present invention.

Phenol resin for use in the present invention is resol-type phenol resinor together with novolak-type phenol resin. Resol-type phenol resin foruse for this purpose is a product obtained by condensation reactionbetween phenols and formaldehyde in the presence of an alkalinecatalyst. The phenols for use in the condensation reaction includephenols having two or three replaceable nuclear hydrogen atoms at the o-and/or p-positions in respect to the phenolic hydroxyl group of phenol,p-cresol, m-cresol, p-t-butylphenol, etc., or their mixtures. Thealkaline catalyst for use for this purpose includes ammonia, alkalinemetal hydroxides, magnesium hydroxide, etc. Resol-type phenol resinsproduced from a mixture of m-cresol and p-cresol, and formaldehyde arepreferably used.

Novolak-type phenol resin for use for this purpose is a product obtainedby condensation reaction between phenols and formaldehyde in thepresence of an acidic catalyst. The phenols for use in the condensationreaction include phenols having two or three replaceable nuclearhydrogen atoms at the o- and/or p-positions in respect to the phenolichydroxyl group of phenol, p-cresol, m-cresol, p-t-butylphenol, etc., ortheir mixtures. The acidic catalyst for use for this purpose includesoxalic acid, hydrochloric acid, maleic acid, etc.

The unvulcanized nitrile rubber for use in the present invention is anyone of various commercially available nitrile rubbers including thosewith an extremely high nitrile content (nitrile content: 43% or more), ahigh nitrile content (nitrile content: 36 to 42%), an intermediate-highnitrile content (nitrile content: 31 to 35%), an intermediate nitrilecontent (nitrile content: 25 to 30%) and a low nitrile content (nitrilecontent: 24% or less). Preferable is a nitrile rubber with anintermediate-high nitrile content.

The chlorinated polyethylene for use in the present invention ispreferably that of high chlorination type with a chlorine content ofabout 60 to about 70%.

In the present invention, the above-mentioned components are used in thefollowing proportions on the basis of 100 parts by weight ofphenolxylylene resin or phenolbiphenyl resin:

Resol-type phenol resin: about 10 to about 1,000 parts by weight,preferably about 20 to about 400 parts by weight Novolak-type phenolresin: 0 to 1,000 parts by weight, preferably 0 to 100 parts by weightUnvulcanized nitrile rubber: 10 to 1,000 parts by weight, preferably 20to 300 parts by weight Chlorinated polyethylene: 10 to 500 parts byweight, preferably 10 to 200 parts by weight

When the resol-type phenol resin or said resin and the novolak-typephenol resin are in a proportion of more than about 1,000 parts byweight each, the adhesion durability to flon or water is lowered,whereas when the resol-type phenol resin is in a proportion of less thanabout 10 parts by weight the initial adhesiveness with the metal islowered. When the unvulcani-zed nitrile rubber is used in a proportionof more than 1,000 parts by weight, the adhesiveness with the metal islowered and also the viscosity is much increased, causing troubles ofapplication work, whereas in a proportion of less than 10 parts byweight the compatibility with the nitrile rubber as an adhesioncounterpart is lowered, resulting in an adhesion failure. When thechlorinated polyethylene is in a proportion of more than 500 parts byweight, the adhesion layer becomes brittle, resulting in a decrease inthe strength, whereas in a proportion of less than 10 parts by weight,the reactivity with the rubber is lowered, resulting in pooradhesiveness.

The vulcanizable adhesive composition comprising these components asessential components can be prepared in a liquid state by dissolving thecomponents into a single organic solvent such as a ketone (e.g. methylethyl ketone, methyl isobutyl ketone, etc.) or an aromatic hydrocarbon(e.g. toluene, xylene, etc.) or a mixture thereof to make a solidconcentration of 3 to 10 wt. %.

Vulcanization adhesion of the present vulcanizable adhesive compositioncomprising the above-mentioned components is carried out by applying thevulcanizable adhesive composition to a metal such as mild steel,stainless steel, aluminum, aluminum die cast, brass, zinc, etc.,generally to a metal plate, followed by air drying at room temperatureand drying at about 100° to about 200° C. for about 5 to about 30minutes, bringing an unvulcanized, compounded (hydrogenated) nitrilerubber in contact therewith, and pressure vulcanizing at about 150° toabout 200° C., i.e. vulcanization temperature of the (hydrogenated)nitrile rubber.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will be described below, referring to Examples,where amounts are shown by parts by weight, and amounts in parenthesesare shown by parts by weight of solid matters.

EXAMPLE 1

Phenolxylylene resin (MR-7800, a product of  143(100) Meiwa Kasei Co.,Ltd; solid content: 70%) Resol-type phenol resin (AF-2639L, a product of 67(40) Dainippon Ink & Chemicals, Inc.; solid content: 60%)Unvulcanized nitrile rubber (N-237, a product of  40 Japan SyntheticRubber Co., Ltd.) Chlorinated polyethylene (Z-200, a product of DaisoCo.,  20 Ltd., Chlorine content: 67%) Methyl ethyl ketone 1865 Toluene1865

EXAMPLE 2

Phenolxylylene resin (MR-7800)  143(100) Cresol-modified novolak-typephenol resin (KA-1053L,  20(8) a product of Dainippon Ink & Chemicals,Inc.; solid content: 40%) Resol-type phenol resin (AF-2639L)  53(32)Unvulcanized nitrile rubber (N-237)  40 Chlorinated polyethylene (Z-200) 20 Methyl ethyl ketone 1862 Toluene 1862

EXAMPLE 3

Phenolbiphenyl resin (MR-7851, a product of  143(100) Meiwa Kasei Co.,Ltd.; solid content: 70%) Resol-type phenol resin (AF-2639L)  67(40)Unvulcanized nitrile rubber (N-237)  40 Chlorinated polyethylene (Z-200) 20 Methyl ethyl ketone 1865 Toluene 1865

EXAMPLE 4

Phenolbiphenyl resin (MR-7851)  143(100) Cresol-modified novolak-typephenol resin (KA-1053L)  20(8) Resol-type phenol resin (AF-2639L) 53(32) Unvulcanized nitrile rubber (N-237)  40 Chlorinated polyethylene(Z-200)  20 Methyl ethyl ketone 1862 Toluene 1862

COMPARATIVE EXAMPLE 1

Resol-type phenol resin (AF-2639L) 167(100) Unvulcanized nitrile rubber(N-237)  28 Chlorinated polyethylene (Z-200)  14 Methyl ethyl ketone 916Toluene 916

COMPARATIVE EXAMPLE 2

Resol-type phenol resin (AF-2639L)  167(100) Cresol novolak-type epoxyresin (Epikron N695, a  40 product of Dainippon Ink & Chemicals, Inc.)Unvulcanized nitrile rubber (N-237)  40 Chlorinated polyethylene (Z-200) 20 Methyl ethyl ketone 1867 Toluene 1867

COMPARATIVE EXAMPLE 3

Cresol-modified novolak-type phenol resin (KA-1053L)  250(100)Resol-type phenol resin (AF-2639L)  167(100) Unvulcanized nitrile rubber(N-237)  68 Chlorinated polyethylene (Z-200)  29 Methyl ethyl ketone2618 Toluene 2618

COMPARATIVE EXAMPLE 4 Chlorinated Rubber-based Adhesive (Chemlok 252X, aProduct of Rhode Far East Co.)

Vulcanizable adhesive compositions comprising the foregoing componentsof Examples 1 to 4 and Comparative Examples 1 to 4 were applied to zincphosphate-treated mild steel sheets, respectively, air dried while beingleft standing at room temperature for 10 minutes and then subjected tobaking treatment at a baking temperature of 150° C. for 10 minutes.

Unvulcanized hydrogenated nitrile rubber compounds of the followingComposition 1 to 3 (unit: parts by weight) were brought into contactwith the vulcanizable adhesive-baked mild steel sheets, respectively,and subjected to pressure vulcanization at 180° C. for 6 minutes. Theresulting vulcanization adhesion products were subjected to an initialadhesiveness test, a water resistance test, a PAG resistance test and aflon resistance test.

Initial adhesiveness test: JIS K6256 90° peeling test Water resistancetest: JIS K6256 90° peeling test pieces are dipped in warm water at 80°C., and, 100 hours after the dipping, subjected to the peeling test PAGresistance test: JIS K6256 90° peeling test pieces are dipped in PAG(polyalkylene glycol) oil at 150° C. and, 100 hours after the dipping,subjected to the peeling test Flon resistance test: A sample obtained bypressure vulcanization molding of a 0.5 mm-thick rubber sheet on anadhesive-coated metal plate for JIS K6256 90° peeling is placed in apressure vessel, into which a flon gas (R134a) is injected After beingleft standing in the circumstances at 40° C. for 24 hours, the sample istaken out of the vessel and heated in an oven at 150° C. for one hourNumber of foaming points generated on the adhesion boundary by the flongas is to be counted

(Hydrogenated nitrile rubber Compositions 1 to 3)

Compo- Compo- Compo- sition 1 sition 2 sition 3 HNBR (Zetpol 2020 aproduct of Nippon 100 100 Zeon Co., Ltd.; CN36%) HNBR (Zetpol 1020, aproduct of Nippon 100 Zeon Co., Ltd.; CN44%) N990 carbon black 10 140SRF carbon black 51 White carbon (Specific surface area 70 m²/g) 60 Zincoxide 5 5 5 Stearic acid 0.5 0.5 0.5 Diphenylamine-based antioxidant 1.51.5 0.5 (Nocrack CD, a product of Ouchi-Shinko Kagaku K.K.)Imidazole-based antioxidant 1.5 1.5 2 (Nocrack MB, a product ofOuchi-Shinko Kagaku K.K.) 1,3-di(t-butylperoxyisopropyl) benzene 10 1010 (concentration 40%) (Peroxymon F40, a product of NOF Corp.) Adipicacid-based plasticizer (RS107, a pro- 10 10 2 duct of Asahi Denka KogyoK.K.) Vinyl silane compound (A151, a product of 2 Nippon Unicar Co.,Ltd.) Processing aid (Vestenemar 8012, a product 5 5 of Huels Co., Ltd.)

The results are shown in the following Tables 1 to 3.

TABLE 1 (Compound 1) Example Comp. Ex. 1 2 3 4 1 2 3 4 [Initialadhesiveness test] Adhesion strength 18.8 18.8 18.6 18.9 8.8 6.5 18.818.9 (N/mm) Percent rubber 100 100 100 100 10 0 100 100 retaining (%)[Water resistance test] Adhesion strength 18.5 18.5 18.5 18.5 — — 18.510.1 (N/mm) Percent rubber 100 100 100 100 — — 100 0 retaining (%) [PAGresistance test] Adhesion strength 17.5 17.5 17.5 17.5 — — 17.5 16.5(N/mm) Percent rubber 100 100 100 100 — — 100 80 retaining (%) [Flonresistance test] Number of 0 0 0 0 — — 6 20 foaming points

TABLE 2 (Compound 2) Example Comp. Ex. 1 2 3 4 1 2 3 4 [Initialadhesiveness test] Adhesion 17.9 18.1 17.9 17.8 17.8 17.7 17.9 17.9strength (N/mm) Percent rubber 100 100 100 100 100 100 100 100 retaining(%) [Water resistance test] Adhesion 17.5 17.3 17.1 17.3 11.1 17.1 17.58.5 strength (N/mm) Percent rubber 100 95 100 90 20 70 70 0 retaining(%) [PAG resistance test] Adhesion 17.5 17.5 17.5 17.5 17.3 16.5 17.516.5 strength (N/mm) Percent rubber 100 100 100 100 100 90 100 70retaining (%) [Flon resistance test] Number of 0 0 0 0 3 7 5 15 foamingpoints

TABLE 3 (Compound 3) Example Comp. Ex. 1 2 3 4 1 2 3 4 [Initialadhesiveness test] Adhesion 17.1 17.2 17.1 17.3 17.0 17.2 17.2 17.2strength (N/mm) Percent rubber 100 100 100 100 100 100 100 100 retaining(%) [Water resistance test] Adhesion 16.9 16.8 16.9 16.9 14.5 15.9 156.5 strength (N/mm) Percent rubber 100 100 100 100 50 80 60 0 retaining(%) [PAG resistance test] Adhesion 17 16.8 16.9 16.9 16.4 16.9 16.9 12strength (N/mm) Percent rubber 100 100 100 100 90 100 100 60 retaining(%) [Flon resistance test] Number of 0 0 0 0 1 3 6 10 foaming points

INDUSTRIAL UTILITY

In the vulcanization adhesion between a metal and (hydrogenated) nitrilerubber, the present vulcanizable adhesive composition is effectivelyapplied to (hydrogenated) nitrile rubber with a nitrile content of 18 to48%, and has a suppression effect on a decrease in the adhesiveness evenif exposed to a flon gas or dipped in polyalkylene glycol or water for along time. Integrated seal parts made up of a metal and (hydrogenated)nitrile rubber, as vulcanization adhered to each other by the presentvulcanizable adhesive composition can be effectively used as cryogenicliquid seals, etc.

1. A vulcanizable adhesive composition for use in providingvulcanization adhesion between a metal and nitrile rubber with a nitrilecontent of 18 to 48% or between a metal and a hydrogenated nitrilerubber with a nitrile content of 18 to 48%, said vulcanizable adhesivecomposition, comprising 100 parts by weight of methylol group-containingphenolxylylene resin as a polycondensation product between1,4-bis(alkoxymethyl)benzene and phenol having at least one methylolgroup at the 2,4-positions or methylol group-containing phenolbiphenylas a polycondensation product between 4,4′-bis(alkoxymethyl)bisphenyland phenol having at least one methylol group at the 2,4-positions, 10to 1,000 parts by weight of resol-type phenol resin, 0 to 1,000 parts byweight of novolak-type resin, 10 to 1,000 parts by weight ofunvulcanized nitrile rubber and 10 to 500 parts by weight of chlorinatedpolyethylene.
 2. A vulcanizable adhesive composition according to claim1, as prepared in the form of an organic solvent solution.
 3. Anintegrated seal element which comprises a metal and nitrile rubber or ametal and hydrogenated nitrile rubber, adhered together by vulcanizationof the vulcanizable adhesive composition according to claim
 1. 4. Anintegrated seal element which comprises a metal and nitrile rubber or ametal and hydrogenated nitrile rubber that are adhered together byvulcanization of the vulcanizable adhesive composition according toclaim 1, wherein an adhesive characteristic of the composition isresistant to cryogenic fluids.
 5. An integrated seal element whichcomprises a metal and nitrile rubber or a metal and hydrogenated nitrilerubber adhered together by vulcanization of the vulcanizable adhesivecomposition according to claim
 2. 6. An integrated seal element whichcomprises a metal and nitrile rubber or a metal and hydrogenated nitrilerubber that are adhered together by vulcanization of the vulcanizableadhesive composition according to claim 2, wherein an adhesivecharacteristic of the composition is resistant to cryogenic fluids. 7.In a sealing element used to provide a seal against cryogenic fluids,the improvement wherein the sealing element comprises a metal andnitrile rubber or a metal and hydrogenated nitrile rubber that areadhered together by vulcanization of the vulcanizable adhesivecomposition according to claim
 1. 8. In a sealing element used toprovide a seal against cryogenic fluids, the improvement wherein thesealing element comprises a metal and nitrile rubber or a metal andhydrogenated nitrile rubber that are adhered together by vulcanizationof the vulcanizable adhesive composition according to claim 2.